Automatic telephone-exchange system.



A, E. LU'NDELL. AUTOMATIC TELEPHONE EXCHANGE SYSLTEM.

APPLICTION FILED )UNE 8, |9l5.

Ialtvntwl Sept. ,5, 1916 /nVer/for.' ,l1/ber) f. LJ/7de abandoning the call.

ini {QQ ALBEN E. LUNDELL, OF NEW YORK, N. Y., SSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

To all whom it may concern Be it known that I, ALBEN E. LUNDELL, a citizen of the United States, residing at New York, in the county of Bronx and State of New York, have invented certain new and useful Improvements in Automatic TelephoneExchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems employing machine switching, and more particularly to what are known as two-wire systems. In such systems it is customary to employ two slow acting relays for controlling a selector, one energized by impulses from the front contact of the stepping relay to maintain the release circuit open, and the other by impulses from the back contact of the steppmg relay, and thus, at the termination of the line circuit interruptions caused by the sender transmitting the digit of the called number involved in the operation ofthe selector in question, becoming denerglzed to operate an electromagnetic switch which brings about the necessary circuit changes to initiate the trunk hunting operation.

it is the' object of this invention to provide aneiiicient selector circuitofthis character wherein a single relay performs the functions which hitherto required the two slow relays above mentioned.

ln accordance with this invention a relay, slow to attract its armatures-` is employed, and is connected to both `iront and back contacts of the stepping relay. rthisrelay is so constructed that it wiil not become sufciently magnetized to attract its armatures as long as the sender is interrupting the line circuit, and consequentiy intermittently energizing the stepping reiay, but will attract its armatures when the stepping reiay closes its iront or back Contact a relatively long interval.

The circuit of the release magnet of the selector leads by Way ofk a front Contact of the slowly operating relay and a back contact of the stepping relay.. Thus, it when the slowly operating relay energizes, the stepping relay is denergized, the selector will be released. This would be the case if the calling party hangs up his receiver, thus if, on the contrary, the stepping relay is energized when the slowly operating relay encrgiaes, an electro- Specication of Letters Patent.

accompanying drawing which shows dia-v grammaticallyonly so much of a telephone system as is necessary for an understanding of the invention.

The calling line, whose substation is designated A, may be extended to the first selector shown in any well-known manner, as for example, by one or more line finders. Assuming, therefore, that' the calling line has, upon the removal of the receiver at substation A, been extended by a finder to the first selector shown. thereat-is then energized over the following circuit: free pole of' battery, left-hand winding of said relay, conductor 1l, side switch arm l2 andv its first Contact, conductory 13, line conductor 1G, through the telephone set at substation A, sender S, line conductor 17, conductor 18, side switch arm 22 and its first contact, conductor V23, right-hand Winding of relay 10 to ground. Relay 10, upon energizing, closes at its armature and front contact a circuitfor primary stepping magnet 25-Vas follows: free pole of battery, magnet 25, conductors 28,l 29, contact springl 26 and its normal left contact, conductor 27, armature and front contact of relay 10 to ground. The primary ,magnet 25 is energized and steps the selector shaft (not shown) one step in a primary direction, and transfers contact spring 26 from its normal left contact into a neutral position between its right and left contacts. This is an idle step on the part of the selector switch shaft, and is not a part of its selecting operation. The relay 24, while in parallel with magnet 25, is so; constructed as to attract its armatures only after a predetermined interval after the closure of its circuit, and does not become energized when relay 10 closes its front contact, since the spring 26 immediately thereafter opens its circuit.

ihe subscriber at substation A now operates the sender S a number of times, corre.

spending to the first digit of the wanted Patented Sept. 5,1916.

Application filed June 8, 1915. Serial No. 32,824. l

The stepping relay 10` til@ 1gization only.

it ,sends an impulse to the primary magnet 25 over the following circuit: free pole fof battery, stepping magnet 25, conductors 28. 29, 31, top armature and'back contact of slowly'operating relay 24, conductor 32, left armature and back contact of side switch magnet 33, conductor 34, spring 35, (closed o-n the first primary step to its right contact), conductor 3G, armature and back contact of relay 10 to ground. lliagnet 25 thereupon steps the selector brushes 37, 38, 39 in a primary direction into operative relation to the group of trunks corresponding to this digit of the Wanted number. lll/Then the relay 10 remains energized, after the sender S has been restored, it closes its front contact for a suflicient length of time to energize the slowly operating relay 24 over the following circuit: free pole of battery, lower winding of relay 24, contact spring 40 (closed until the. first secondary step of the selector shaft has been taken), conductor 41, contact spring 26 and its right contact (closed on the second primary step of the shaft), conductor 27, right armature and front contact of relay 10 to ground. The relay 24, by -closing its lower armature and front Contact, energizes the magnet 33, which is the escapement magnet of the side or steering switch, over the rfollowing circuit: free pole of battery, escapement magnet 33, conductor 42, side switch arm 43 and its first contact, conductorel, lower armature and front contact of relay 24, conductor 45, right armature and back Contact of release magnet 4G, primary off-normal spring PON to ground.

rlfhe side'switch magnet 33 is so arranged that it releases the side switch upon its enerlln position 2 of the side switch its arm 50 closes a circuit for causing the secondary stepping magnet automatically to step the selector brushes 37, 38, 39 over the selected group of trunks in search .of an idle trunk therein. rlhis circuit is as `the ,side switch magnet 33 in circuit with the test brush .39 of the selector to .act as a test relay. ldle trunks are those upon Whose test terminals 52 ground is present. When the test bruslr39, therefore, encounters a test terminal 52; which is grounded at the hack contact of the stepping relay 53 of an idle second selector, the si lswitch magnet 33 lenergizes, opening the stepping circuit of secondary magnet" 48 at its right armature and back contact, and releasing the side switch to osition 3. lln position 3 of the side switcli the calling line is connected through to the second selector thus seized, Whose brushes 54e, 55 only are shown. The

lineages side switch arms 22', 12 belong to the side switch of this selector. Since this selector is identical with the first selector, only so much is shown as is necessary to comprehend the operation of the first selector. Continuing, therefore, when the side switch arms 22, 12 of the first selector move into position 3, the stepping relay 53 of the second selector is energized over the following circuit: free pole of battery, left winding'of relay 53, side switch arm 12 of this selector and its first Contact, contact 6G, brush 38, conductor 63, brush 12 and its third contact, conductors 13, 16. telephone set at substation A, conductors 17, 18, brush 22 and its third contact, conductor (3T, brush 37, terminal 65, side switch arm 22 of the second selector and its first contact, conductor 71, right winding of a stepping relay to ground. rl`his relay at its armature and back contact removes ground from the multiple test terminals 52, thus rendering the seized trunk unselectable by other selectors. lln moving from positions 2 to 3, the side switch arms 22, 12 of the first selector cut off' the stepping relay 10 from the line conductors 13, 13. 'l`he armature of said relay "thereupon, at its back contact, closes the following circuit for relay 24;:

.free pole of battery, upper winding of relay 24, conductor 32, left armature and back Contact of magnet 33, conductor 34, spring 35 and its right contact, conductor 36, armature and back contact of relay 1() to ground. 'llhe relay 24 thereupon energizes, closing the following circuit for the magnet 33: free pole of battery, magnetI 33, conductor l2, arm t3 and its third contact, conductor 44, lower armature and front Contact of rela-y 24, conductor 45, right armature and -back contact of release magnet 4G, spring PGN to ground. rll`he rst selector side switch thereupon lnoves into position si, the arm 59 preparing the release circuit. lt will be noted that since the side switch magnet cannot be moved out of position 3 until the relay 2l closes its front contact, and since this relay is slow to close such contact due to its construction, it follows that ground will be removed from conductor 62 by relay 53, (energized as arms 22, l2 move into position 3) before the arm 59 engages its fourth contact connected to said conductor 62. rl`hus there is no danger of premature release. The second selector is now operated in a manner similar to that already described, under control of the calling partys sender S, to pick out a connector, whose brushes 56, 57 only are shown, having access to the desired line, which connector is in turn operated by the subscriber inthe well-known manner to conneet with the wanted line, after which the line is tested and rung if idle, or the connector released and a busy signal given back to the calling party if busy.

Referring back to the setting of the first lll@ selector, it will be observed that the relay 24 is provided with two windings. The circuit of the upper winding is controlled at the back contact of the line relay 10. The circuit of the lower winding is controlled at the front contact of the line relaylO. Thus, since this relay 24 is slow to attract itS ar matures, due to its construction, it will only respond when the armature of relay 10 rests on its back or front contact for a predetermined interval of time long enough to energize the relay 24 by the corresponding winding. It followsfrom this that if, after the subscriber has removed hisreceiver and before the selector switch has completed its operation and selected an idle trunk, he replaces it again, in other words, abandonsy the call, the selector is released over the following circuit, due to the energization of saidrelay and the denergized conditionof the stepping relay 10: -free pole of battery, release magnet 46, conductor 58, side switch arm 59 and its front contact, conductor 60, upper armature and front contact of relay 24, conductor 32, left armatureand back contact of side switch magnet 33, conductor 34, contact spring and itsright contact (now closed), conductor 36, armature and back contact of line relay 10, to ground. In case the side switch of the selector is in position 2, that is, in oase the selector switch is trunk hunting, the circuit of release magnet 46 is closed over the following circuit: free pole of battery, release magnet 46, conductor 58, side switch arm 59 and its second contact, secondary off-normal spring SON (closed on the first secondary step of the selector switch), upper armature and front contact of slow relay 24, left*- armature and back contact bf side switch magnet' 33', con,-

ductor 34, contact spring 35, and its right contact (now closed), conductor 36, armature and back contact of line relay l0 to ground. The release magnet,vbylmeans of its right armature and front'cOntact, locks itself up in a circuit controlled. at primary off-normal contact PON, which opens when the selector reaches its normal position, and opens the said locking circuit. 'Assuming however, the connectionhas been set up and the calling subscriber, upon the co'nclusion of the conversation, hangs up his receiver. This causes the release of the connector and second selector, the second selector, in reaching its normal position, placing a ground upon test terminal 52 by the closure of spring 64 thereof (closed only in the normal position of the'selector). This causes the release of the first selector by the closure of the following circuit: free pole of battery, release magnet 46, conductor 58, side `vswitch arm 59 aiid its fourth contactcon duetor 62, test brush 39, test contact 52, conductor 63, contact spring armature and back contact vof relay 53 to ground. Y

The spring 35 of the first selector closes to its left contact when the selector reaches its normal position, and grounds conductor 72 leading back to the finder -or equivalent switch to release the same. f

The relay 24 is so wound that the magf netic field set up therein by the closure of the circuit through the stepping relay armature and its front Contact and the upper winding is opposite to that set up by the closure of the circuity through the said armature, its back contact and the lower winding, in order to avoid the possibility of false operation of the relay.

What is claimed is:

1. In a machine-switching telephone eX- c'hange system, the combination with a selector, a stepping relay associated therewith,

a sender for intermittently operating the same, a stepping magnet controlled by said stepping relay and a release magnet, of a slowly operating relay, a circuit therefor change system, the combination with a selector, a stepping relay associated therewith, a stepping magnet controlled thereby, a sender for intermittently operating said stepping relay, a steering switch, a'control magnet therefor and a release magnet, of a slowly operating relay, a circuit therefor controlled at the front contact of said stepping relay, another circuit therefor controlled at the back contact of said stepping relay, a circuit for lsaid release magnet controlled at a front contact of said slowly operating relay and aback contact of said stepping relay, and a circuit for said steering switch magnet controlled at a front contact of said lslowly operating relay.

' 3. In a machine switching telephone ex' slowly operating relay, a circuit controlled at the front contact ofl said stepping relay including one of saidwindings, another circuity controlled at'the back contactr of said stepping relay including the other winding, said slowly operating relay having a pair of armatures,.one'ofwhich is adaptedl when attracted to close" the circuit of saidl steering switch control magnet, and the other being adapted when attracted to close one break in said release circuit, another break in this circuit being closed `at the back contact of the armature of said stepping relay.

f4. In a machine switching telephone exchange system, the combination with a selector, a stepping relay associated therewith, a sender for intermittently operating the same, a stepping magnet controlled by said stepping relay, and a release magnet, of a double Wound slowly operating relay a circuit controlled at the front contact of said stepping relay including one of said windings, another circuit controlled at the back Contact ofl said relay including the other winding, the magnetic eld set up in said relay by the closure of one of said circuits being opposite to that set up by the closure of the other, and a circuit for said release magnet controlled at a front contact of said slowly operating relay and the-back contact of said stepping relay.

mames 5. ln a machine switching telephone exchange system, the combination with a selector, a stepping relay associated therewith, a sender for intermittently operating the same, a stepping magnet controlled by said stepping relay and a release magnet, of a slow relay controlled by said stepping relay and constructed and arranged to remain inoperative while said Vsender is operating, and to `operate when the intermittent actuation of said stepping relay is discontinued, and a circuit for said release magnet controlled at a front contact of said slow relay and a back contact of said stepping relay.

ln witnesss whereof, ll hereunto subscribe my name `this 5th day of June A. D., 1915.

ALBEN n. Lnitnnnn 

